For more than a century, it has been understood that breast cancers spread from the breast primarily by entering into and passing along lymphatic channels draining the breast. These channels pass into the armpit, into the skin and through the chest wall. Tumor spread is partly impeded by the presence of lymph nodes; in which tumor cells can remain and grow, or pass though and into the blood stream. Near the turn of the century, William Halsted proved the utility of this knowledge by surgically removing all possible lymphatic channels in addition to removing the breast. While this had the disadvantage of being a fairly mutilating procedure, he was able to reduce the rate of local recurrence of breast cancer to six percent from the previously reported recurrence rate of fifty to eighty-five percent when only the breast was removed.
Since the time of Halsted, surgical approaches have moved away from radical techniques toward tissue-sparing approaches. With the ability of earlier detection, minimal surgery; coupled with radiation and/or chemotherapy, has achieved similar results in preventing local recurrence. The problem of detection of tumor spread remains. Often, women who appear to have early stage disease will die of metastatic cancer despite a lack of evidence of spread. Therefore, breast cancer has been called a "systemic disease." This is most likely because cancer cells can spread undetected through lymphatic pathways; often early in the disease.
The primary determinant of survival in breast cancer is the presence or absence of tumor cells within the axillary (armpit) lymph nodes. Axillary nodes are removed to detect tumor spread and prevent recurrence. Tumor spread into other lymphatics that drain the breast is still undetectable, and probably accounts for cases of metastasis when the axillary lymph nodes are free of cancer. Lymphatic flow is determined by pressure and osmolar gradients. Increases in interstitial fluid or in externally applied pressure will enhance lymphatic flow. Entry of tumor cells into lymphatics is an active process of the tumor cells. Once in the lymphatic channels, tumor cells are carried along passively by the flow of lymphatic fluid. Any increase in interstitial fluid or pressure will, therefore, increase the rate of tumor spread.
Breast cancer can recur many years after initial treatment. Presumably, this is because of the undetectable spread of small numbers of tumor cells. While it has been known for many years that cutting into tumors can enhance their spread, present techniques of needle and core biopsies do just this. It has been claimed that these maneuvers don't spread cancer; however, the truth of these claims might not be apparent for many years.
Presently, the modalities of palpation, x-ray, ultrasound, and MRI are used to detect human breast cancers. Some of these techniques are used also for image-guided biopsy of breast tissue. Mammography is the mainstay of current early detection of breast cancer. This technique requires the forceful compression of the breast between plates to achieve acceptable images. Other known detection techniques, as previously mentioned, include ultrasound, magnetic resonance imaging (hereinafter "MRI"), and computerized tomography (hereinafter "CT"). Ultrasound images of the breast are obtained using a probe placed directly against the skin of the breast. MRI images are made by placing the breast in a magnetic field, between coils or hanging into a well that is surrounded by a coil. The principles of MRI are known to those of ordinary skill in the art. A description may be found in U.S. Pat. No. 5,437,280 to Hussman entitled "Magnetic Resonance Breast Localizer" which is hereby incorporated by reference in its entirety. Stereotactic biopsy techniques are done in a similar fashion; with a patient lying prone, with the breast hanging through a hole in the table. All these methods have shortcomings related to the flaccid nature of the breast which leads to difficulty in manipulating and orienting the organ. Additionally, some of these methods are very uncomfortable for the patient. The pain often associated with the forceful compression of the breast between plates in mammography being a prime example.
Early detection of breast cancers has spurred increasing interest in early intervention. Open biopsy techniques have given way to more image-guided biopsy methods which currently require forceful compression of the breast for stabilization, and require the forceful passage of instruments into the breast which often cause considerable bleeding; especially once the compression has been released. The tissue is in a distorted state and accurate removal of a specific volume of breast tissue is difficult. Present techniques for image-guided biopsy of the breast are limited by the size of the lesion to be removed, and by continuing challenges of bleeding and spread of tumor cells. Removal of lesions greater than a centimeter is generally not possible by these methods.
One object of the present invention is to allow for improved imaging and intervention in diagnosis and treatment of cancer, particularly early stage human breast cancer. Another object of the present invention is to allow for the accurate removal of tissue in a minimally bleeding or bloodless field.